WHO 2016 classification of Astrocytic tumors:
| Type | WHO Histologic Grade | |
| Diffuse astrocytic tumors | Diffuse astrocytoma IDH-mutant |
II |
Anaplastic astrocytoma IDH-mutant |
III | |
Glioblastoma IDH-wild type |
IV | |
Glioblastoma IDH-mutant |
IV | |
Diffuse midline glioma H3 K27M-mutant |
IV | |
Diffuse midline glioma H3 K27M-mutant |
||
| Other astrocytic tumors | Pilocytic astrocytoma | I |
| Pilomyxoid astrocytoma | uncertain | |
| Pleomorphic xanthroastrocytoma | II | |
| Anaplastic pleomorphic xanthoastrocytoma | III | |
| Subependymal giant cell astrocytoma | I |
Low Grade Astrocytomas (LGA)
Localized
Grow slowly over a long period of time
Most LGA are of two types:
1. Pilocytic astrocytoma (PA)
- World Health Organization [WHO] grade I
- Circumscribed
- Homogeneously neoplastic
- Low potential for tissue infiltration or malignant degeneration
- Lacks p53 changes, but may show loss of chromosome 17q in the region of
the NF1 gene
2. Diffuse fibrillary astrocytoma (DA)
- WHO grade II
- Invasive tumor
- Tendency to undergo malignant change (esp in adults)
- Genetically distinct - associated frequently with p53 mutations or occasionally
with loss of heterozygosity on chromosome 10p.
Other Low-Grade Astrocytomas:
- Pleomorphic Xanthoastrocytoma (PXA)
- Form of astrocytoma unique to children
- More common in late childhood and early adolescence
- Subependymal Giant Cell Astrocytoma
- Dysembryoplastic Neuroepithelial Tumor (DNET)
- some would argue that these are neuroepithelial tumors rather than gliomas
- Ganglioglioma
- Oligodendroglioma
- Desmoplastic infantile ganglioglioma
High-grade astrocytomas
- Worse prognosis than LGA
- Higher rate of neuraxis dissemination
- Grow rapidly
- Two main classes of high grade astrocytomas:
- anaplastic astrocytomas
- glioblastoma multiforme
Characteristics of High Grade Astrocytomas:
|
Anaplastic Astrocytoma |
Glioblastoma Multiforme (GBM) |
Patient Age |
Uncommon in children
Tend to occur in adults (median age 40yrs) |
Uncommon in children
Tend to occur in adults (median age 45-70yrs). |
Tumor Location |
Cerebral hemispheres Brain stem |
Subcortical white matter of cerebral hemispheres |
Histology |
Increase in cellularity
Nuclear pleomorphism
Hyperchromasia
May have mitosis & vascular proliferation
No necrosis
|
Dense cellularity
Mitotic figures
Vascular proliferation
Necrosis is present |
Prognosis |
High incidence of progression to glioblastoma |
Very poor prognosis |
External Link:
Overview of Astrocytomas at the Atlas of Genetics and Cytogenetics in Haematology and Oncology
